Spiral staircases

ABSTRACT

A spiral staircase is built up from modular fabricated step units superimposed upon one another without necessitating the use of an independent continuous central newel column. Each step unit essentially comprises a tubular newel boss having a vertical axis, attached to a tread which extends laterally and radially in a horizontal plane. The step units are secured to each other so that their bosses together constitute the central newel post of the staircase. The staircase can be erected from a base level, after the lowermost step unit has been firmly secured, and while it is being erected, the builders can use those units which have already been assembled for the purpose of carrying up further step units.

United States Patent 9 MacKay 5] June 6, 1972 [54] SPIRAL STAIRCASES 3,483,707 12/1969 Meheen ..52 724 [72] Inventor: Donald R. H. MacKay, Britannia Works, FOREIGN PATENTS OR LI O East Road, Cambridge, England 1,540,609 8/1968 France ..52/187 [221 1970 392,028 9 1965 Switzerland ..52/187 21 App]. No.2 12,377

Primary Examiner.lohn E. Murtagh Att0rneyStevens, Davis, Miller & Mosher [30] Foreign Application Priority Data Feb. 18, 1969 Great Britain ..8,696/69 1 ABSTRACT A spiral staircase is built'up from modular fabricated step [52] U.S.Cl ..52/187,52/726 units Superimposed upbn one another without necessitating [5 l] r the use of an independent continuous central newel column [58] d 0 Search 3 1,23 3 Each step unit essentially comprises a tubular newel boss hav- 1 2 ing a vertical axis, attached to a tread which extends laterally and radially in a horizontal plane. The step units are secured [56] References Cned to each other so that their bosses together constitute the cen- UNn-ED STATES PATENTS tral newel post of the staircase. The staircase can be erected 1 from a base level, after the lowermost step unit has been firmly 52,922 2/1866 Vlhdmayer ..52/187 secured, and while i is being erected, the builders can use 111,187 1/ 1871 Flflk those units which have already been assembled for the pur- 208'326 9/1378 pose of carrying up further step units. 1,726,133 8/1929 Wilson 1 ,834,535 12/ l 931 Riemenschweider ..52/726 15 Claims, 12 Drawing Figures PATENTEDJUR 5 I972 SHEET 3 0F 3 FIG.|2

FIGS

SPIRAL STAIRCASES This invention relates to vertebrate spiral staircases by which is meant spiral staircases comprising modular step units, in which all or the majority of step units of a flight are identical with or closely similar to each other, and are secured together without the use of a continuous newel post extending for the full height of the staircase or flight.

Spiral staircases assembled from step units are already in use. Known forms of construction involve step-units in which the stair tread extends laterally and radially from a tubular boss, the step-units being united by a central, vertical, cylindrical newel column (normally tubular) on which they are threaded, the column extending to the full height of the complete staircase. This construction makes it necessary to raise each step-unit to the top of the column before lowering it into place. Further, in our experience, unless the step-units and the column are accurately dimensioned and machined, and for this reason unnecessarily costly, assembly involved, in addition to the need for hoisting gear, difficulties in threading successive step-units on to and down the central column.

It is the purpose of this invention to provide a spiral staircase constructed from single step-units of an improved form, which permits the simple and rapid assembly of one-step unit directly on another without the use of acontinuous newel post extending from the full height of the staircase or flight, and having the extending treads radiating at any desired angular relationship until the required total height of ascent has been achieved. The invention also includes the improved step-units themselves.

According to the invention a fabricated modular step unit for a vertebrate spiral staircase (as herein defined) comprises a tubular newel boss to which is attached a radially extending tread, each end face of the boss lying generally in a plane at right angles to the axis of the boss and parallel with the plane of the tread face and being provided with means for securing the boss of any unit disposed intennediately in a flight of step units to the immediately adjacent bosses above and below it.

When the rise of each flight is known in advance, the axial length of the boss can be made equal to this; when the rise is not known, the boss can be made less in length and separating rings or discs can be interposed to increase the effective length by the desired amount.

The cross section of the tubular boss may be circular or it may be polygonal with not fewer than five sides.

In one convenient construction the boss is closed at one end by a circular flat plat having a central hole which permits one step unit to be secured to an adjacent unit, either by a bolt and nut or, by tapping one of the holes, by means of a bolt alone: conveniently access to the inside of the boss is provided by a hole in .the side wall of the boss. If a socket headed screw is used this can be turned by a key passed through the opposite hole.

For more secure fixing of a step unit to an adjacent member more than one holding screw may be used and by providing arcuate holes in one end plate to correspond with normal holes in the opposite end plate the radial angle between adjacent treads may be varied.

Alignment between two bosses during assembly may be facilitated by recessing one end plate and allowing the other to protrude, thus providing a spigot and socket type of engagement. Alternatively in cases where both end plates are recessed, a loose ring may be inserted to provide similar spigot and socket engagement.

Instead of a disc type of end plate a cross member may be used, conveniently rectangular in section, at each end of the boss, the outer faces at right angles to the axis of the boss and each with a central hole for bolting one unit to a base member, an adjacent step member or a landing. With this arrangement access to the inside of the boss can be obtained by the side of the cross member so that a hole in the side of the boss may not be necessary.

By recessing one cross member and allowing the other to protrude sufficiently spigot and socket engagement is pro vided to ensure true alignment when assembling the staircase.

The invention is not limited as to the materials which may be used in the construction of the step units. These may be entirely of metal, as they normally will be for staircases to be used as fire escapes. The treads may conveniently be folded up from sheet metal into tapered channel form; the upper surface of the tread may be constructed so as to reduce the danger of slipping, as by the use of expanded or otherwise ridged metal.

Alternatively the treads may be made wholly or in part of wood or reinforced plastics.

A metal tread may be welded directly to the boss or lugs may be provided on the boss to which is bolted or riveted or welded the adjacent part of the tread.

The invention includes spiral staircases comprising an assembly of step units each of which is in accordance with the above descriptions and which may, and nonnally will, start from the ground by bolting the lowest step unit to a base plate and have at least one landing to which the units will be bolted. The bosses of the type which are provided with cross members may be filled with concrete or reinforced plastics material poured in in liquid state from time to time as step units are added. Reinforcing wires or rods may be incorporated in the concrete or plastics material. Alternatively, rigidity may be added by encasing the central column formed by the connected bosses with a continuous sleeve of concrete.

The completely erected staircase will normally be provided with balusters and a hand rail. The balusters may conveniently be attached to opposite sides of adjacent treads, either by bolting or riveting them to the sides of the treads or by passing them through holes in the upper surfaces of the treads and securing them to at least one of the treads. When the appropriate parts of the treads are not vertically one above the other, then the balusters will be cranked accordingly.

I A completed staircase comprising an assembly of such stepunits also forms part of the invention, as does the method of assembling the staircase.

This construction of the step units allows a spiral staircase to be assembled by placing and securing the boss of one stepunit to a fixed base, then securing the bosses of successive step units to those of adjacent lower units already in place, interposing platforms as and if needed and topping off with a platform secured to an adjacent fixed structure. When convenient, it is possible to use already assembled step-units for carrying up higher step-units which are to be added and each unit being superimposed upon and attached to the next below it. Intermediate and upper platforms may be affixed to the adjacent step unit bosses in like manner to that in which the bosses of intermediate step units are joined together.

The invention will now be further illustrated by way of example with reference to the accompanying drawings in which:

FIGS. 1, 2 and 3 illustrate one form of step unit according to the invention;

FIGS. 4, 5, 6, 7 and 8 illustrate alternative forms of the central boss component without showing the tread which would be attached to them;

FIG. 9 shows a method of adding strength and rigidity to a spiral staircase comprising step units according to the invention;

FIG. 10 shows one method of attaching balusters for ahandrail to an assembled spiral staircase; and

FIG. 1 1 shows a spigot and socket form of construction.

FIG. 12 is a view of an assembled staircase.

FIG. 1 shows in medial section an all-metal step unit com prising a cylindrical boss 1 with an access hole for a spanner 16 in the side wall and having end disc plates 2 and 3 weldedin so as to leave the boss extending beyond both dises. The upper disc has a central tapped hole 4 while the lower disc has a central clearance hole 5. The tread 7, of tapered channel section, is secured to three lugs on the boss, 8, 9 and 10, by bolts. FIG. 2 views this unit from above and shows, in broken lines, the radial location of the three lugs 8, 9 and 10. FIG. 3 shows how the channel form tread may be made by folding the rectangular metal sheet 11 at right angles along the broken lines 12 and 13.

To assist in aligning one boss upon another during assembly a loose ring 6 is interposed between adjacent bosses.

FIG. 4 illustrates in medial section an alternative construction of boss in which the upper end plate 2 is provided with additional tapped holes such as 17, all equidistant from the center, while the lower plate 3 is provided with arcuate slots 18 through which bolts can be passed and screwed into the tapped holes 17 in the end plate of the adjacent boss at a selected angular relationship of the two bosses.

It will be seen that the lower end plate 3 in FIG. 4 protrudes beyond the end of the boss so as to provide spigot and socket engagement between pairs of bosses.

FIGS. 5 and 6 are end views of the boss shown in FIG. 4.

FIGS. 7 and 8 illustrate a further embodiment of the invention in which, instead of end discs, cross bars 14 and 15 are welded inside the boss, one with a tapped central hole 4, and the other with a central clearance hole 5. The upper cross bar 14 is recessed below the end of the boss while the lower cross bar 15 protrudes sufiiciently to provide spigot and socket type engagement with the adjacent boss.

FIG. 9 shows how a stack of step units as in FIG. 7, forming a spiral staircase can be reinforced progressively during assembly by, first hanging 8" shaped reinforcing metal rods 19 from cross bars and then pouring in fine-aggregate concrete 24 from time to time as the height of the stack increases.

FIG. 9 also shows how, by using socket-headed bolts, these can be turned by means of a key 25 passed through the hole in the cross bar at opposite end of the boss.

FIG-10 illustrates one method by which balusters can be rigidly secured to opposite sides of adjacent treads. The circu lar section baluster post 20 carries a hand rail 21 and is reduced in diameter at 22 so as to pass, first through a hole in the upper tread 7, then through aspacing tube 23 and the lower tread 7 to a fixing nut 24.

FIG. "11 shows an assembly in which each boss has a spigot 25 and a socket 26, the spigot on one boss fitting into the socket on the adjacent boss.

in a further modification, a staircase may be constructed from several superimposed assemblies of step units, each of which is held together by securing means, such as a common, centrally disposed spindle, passing through the assembly.

For example, three step units having the construction of FIG. 1, but with the hole 4 enlarged to the dimensions of the hole5, and having no internal screw threads, may be assembled together on a central spindle as hereinafter described.

The spindle, externally threaded at each end, is slightly longer than the distance between the upper plate 2 of the uppermost unit of the assembly and the lower plate 3 of the lowermost unit of the assembly.

A long, internally threaded nut is attached to one end of the spindle so that this nut extends beyond the spindle, to provide a socket to receive the end of an adjacent spindle. Washers 6 are interposed between the adjacent step units of the assembly and a similar, internally threaded long nut is attached to the other end of the spindle to hold the assembly together. A group of such assemblies may then be joined together to make up the complete flight of a staircase.

I claim:

1. A modular step unit for a vertebrate spiral staircase, comprising: a tubular newel boss; a tread member attached to and radially extending from said newel boss; said newel bosshaving end faces lying generally in a plane at right angles to the axis of said boss and parallel with the plane of the face of said tread, said bosshaving means for securing said boss to immediately adjacent bosses, including, a cross member provided at each end of said boss in a plane at right angles to the axis of said boss, said cross member at least partially closing its adjacent end and extending laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to axially aligned adjacent bosses,

.and wherein said boss defines. means, including at least one aperture in a wall thereof, for providing access for a tool when joining adjacent bosses.

2. A step unit as claimed in claim 1, in which said boss is provided ateach end with a cross member, in a plane at right angles to the axis of said boss, which at least partially closes such end and extends laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to an axially aligned boss of any adjacent unit.

3. A step unit as claimed in claim 2, in which one of said cross members protruding axially beyond oneend of said boss, and said boss at its other end extending axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.

4. A step unit as claimed in claim 2, in which both ends of said boss extend axially beyond said respective cross members.

5. A spiral staircase comprising an assembly of step units according to claim 2, in each of which said step units both ends of said boss extend axially beyond said respective cross members, and in which a free but close fitting sleeve is interposed between adjacent step units and acts to facilitate alignment of said bosses while assembling said staircase.

6. A spiral staircase having a plurality of substantially similar steps, comprising: a plurality of vertically axially aligned tubular bosses, each boss having a member fixed across the inside diameter of said boss adjacent each end thereof, said members having at least one clearance hole defined therein; a bolt element passing through clearance holes of a first said member of a first boss and of the next adjacent member of the next adjacent boss in said plurality of axially aligned bosses; and means, including said bolt member, for axially tightening said first member to said next adjacent member wherein said first boss and said next adjacent boss are tensed between said first member and said next adjacent member; said bosses having complementary ends formed to firmly interengage with each other under compression of said axial tightening means.

7. A staircase as claimed in claim 6, in which the effective axial length of said boss is that of the required rise between adjacent treads.

8. A staircase as claimed in claim 6, in which the effective axial length of said boss is less than the required rise between treads. I

9. A staircase as claimed in claim 6, in which said boss has spigot means at one end and complementary socket means at the other end, said spigot means on one end of any one such boss being adapted to fit into said socket means of an adjacent boss when such bosses are assembled together. 7

10. A spiral staircase comprising an assembly of step units according to claim 6, said step units being secured together with said bosses in axial alignment, and in which separating spacers are disposed between opposing end faces of adjacent bosses, and the vertical height of the rise between adjacent treads of said staircase is equal to the effective axial length of one such boss added to the thickness of one of said spacers.

11. A spiral staircase comprising an assembly of step units according to claim 6, in each of which said step units one of said cross members protrudes axially beyond one end of said boss, and said boss at its other end extends axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.

12. A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly.

13. A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly, and in which rod-like reinforcing elements extending at least between adjacent step units are located within said bosses.

14. A spiral staircase comprising an assembly of step units according to claim 6, said staircase connects adjacent storeys of a building and is attached to the building at least once for each storey. s

15. A vertebrate spiral staircase having superimposed prefabricated modular cantilevered step units one upon another, each step unit comprising a tubular boss, a radially extending tread attached to said boss, each end face of said boss lying generally in a plane at right angles to the axis of the boss and parallel with the plane of the face of the tread, wherein said boss is provided at its upper and lower end respectively with a cross member; said staircase further comprising a newel formed by a plurality of said bosses assembled in adjacent step units in columnar relationship by a screw threaded connection in which a bolt passes through coaxial holes within cross members of at least two adjacent bosses, is carried by and protrudes from one cross member of one such boss and connects with socket means operatively associated with the cross member of the immediately adjacent boss, whereby the tightening of the screw threaded connection supplements axial compression, due to the weight of the assembly between adjacent units without disturbing the radial positioning of the step units; and further wherein each said boss is provided with means, including at least one aperture in a wall, to provide access for a tool when tightening the screw threaded connection, the arrangement being such that a weight loading applied to any intermediate step unit is supported both by the shear stress between the interfaces of the boss of the step unit and the bosses of the immediately adjacent steps above and below that intermediate step, and by tension in each bolt or spindle connecting that boss to the immediately adjacent bosses.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 7, 176 Dated June 6, 1972 Inventofls) Donald Roderick Hubert MacKAY It is certified that error appears in the above-identified patent and that said Letters Patent are. hereby corrected as shown below:

On the title page after section [72] Inventor:" add as the next section:

[73] Assignee: Arthur Guinness Son & Company (Dublin) Limited, a Company incorporated under the Laws of the Public of Ireland Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) USCOMM-DC 60376-P59 U.5 GOVERNMENT PRINTING OFFICE I959 0-366-334 

1. A modular step unit for a vertebrate spiral staircase, comprising: a tubular newel boss; a tread member attached to and radially extending from said newel boss; said newel boss having end faces lying generally in a plane at right angles to the axis of said boss and parallel with the plane of the face of said tread, said boss having means for securing said boss to immediately adjacent bosses, including, a cross member provided at each end of said boss in a plane at right angles to the axis of said boss, said cross member at least partially closing its adjacent end and extending laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to axially aligned adjacent bosses, and wherein said boss defines means, including at least one aperture in a wall thereof, for providing access for a tool when joining adjacent bosses.
 2. A step unit as claimed in claim 1, in which said boss is provided at each end with a cross member, in a plane at right angles to the axis of said boss, which at least partially closes such end and extends laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to an axially aligned boss of any adjacent unit.
 3. A step unit as claimed in claim 2, in which one of said cross members protruding axially beyond one end of said boss, and said boss at its other end extending axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.
 4. A step unit as claimed in claim 2, in which both ends of said boss extend axially beyond said respective cross members.
 5. A spiral staircase comprising an assembly of step units according to claim 2, in each of which said step units both ends of said boss extend axially beyond said respective cross members, and in which a free but close fitting sleeve is interposed between adjacent step units and acts to facilitate alignment of said bosses while assembling said staircase.
 6. A spiral staircase having a plurality of substantially similar steps, comprising: a plurality of vertically axially aligned tubular bosses, each boss having a member fixed across the inside diameter of said boss adjacent each end thereof, said members having at least one clearance hole defined therein; a bolt element passing through clearance holes of a first said member of a first boss and of the next adjacent member of the next adjacent boss in said plurality of axially aligned bosses; and means, including said bolt member, for axially tightening said first member to said next adjacent member wherein said first boss and said next adjacent boss are tensed between said first member and said next adjacent member; said bosses having complementary ends formed to firmly interengage with each other under compression of said axial tightening means.
 7. A staircase as claimed in claim 6, in which the effective axial length of said boss is that of the required rise between adjacent treads.
 8. A staircase as claimed in claim 6, in which the effective axial length of said boss is less than the required rise between treads.
 9. A staircase as claimed in claim 6, in which said boss has spigot means at one end and complementary socket means at the other end, said spigot means on one end of any one such boss being adapted to fit into said socket means of an adjacent boss when such bosses are assembled together.
 10. A spiral staircase comprising an assembly of step units according to claim 6, said step units being secured together with said bosses in axial alignment, and in which separating spacers are disposed between opposing end faces of adjacent bosses, and the vertical height of the rise between adjacent treads of said staircase is equal to the effective axial length of one such boss added to the thickness of one of said spacers.
 11. A spiral staircase comprising an assembly of step units according to claim 6, in each of which said step units one of said cross members protrudes axially beyond one end of said boss, and said boss at its other end extends axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.
 12. A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly.
 13. A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly, and in which rod-like reinforcing elements extending at least between adjacent step units are located within said bosses.
 14. A spiral staircase comprising an assembly of step units according to claim 6, said staircase connects adjacent storeys of a building and is attached to the building at least once for each storey.
 15. A vertebrate spiral staircase having superimposed prefabricated modular cantilevered step units one upon another, each step unit comprising a tubular boss, a radially extending tread attached to said boss, each end face of said boss lying generally in a plane at right angles to the axis of the boss and parallel with the plane of the face of the tread, wherein said boss is provided at its upper and lower end respectively with a cross member; said staircase further comprising a newel formed by a plurality of said bosses assembled in adjacent step units in columnar relationship by a screw threaded connection in which a bolt passes through coaxial holes within cross members of at least two adjacent bosses, is carried by and protrudes from one cross member of one such boss and connects with socket means operatively associated with the cross member of the immediately adjacent boss, whereby the tightening of the screw threaded connection supplements axial compression, due to the weight of the assembly between adjacent units without disturbing the radial positioning of the step units; and further wherein each said boss is provided with means, including at least one aperture in a wall, to provide access for a tool when tightening the screw threaded connection, the arrangement being such that a weight loading applied to any intermediate step unit is supported both by the shear stress between the interfaces of the boss of the step unit and the bosses of the immediately adjacent steps above and below that intermediate step, and by tension in each bolt or spindle connecting that boss to the immediately adjacent bosses. 